Fuel oil compositions containing grafted polymers



United States Patent 3,462,249 FUEL OIL COMPOSITEONS CONTAINING GRAFTED POLYMERS Norman Tunkel, Perth Amboy, N.J., assignor to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Mar. 31, 1967, Ser. No. 627,297 Int. Cl. C101 1/22, N18, N16

US. CI. 44-62 8 Claims ABSTRACT OF THE DISCLOSURE Novel oil soluble ethylene grafted hydrocarbon polymers, copolymers, or terpolymers are added in an amount between about 0.01 and about 10.0 wt. percent to middle distillate fuels, lubricating oils, residual fuels or reduced crude oils to lower their pour points and/or improve their flowability and pumpability.

The present invention relates to the production of ethylene grafted hydrocarbon polymers and copolymers which are particularly useful as pour depressants and flow improvers for hydrocarbon oils, and more especially useful with respect to these properties in compositions of lubricating oils or petroleum middle distillates containing the same. The invention also relates to the production of such polymers, copolymers, and terpolymers, i.e., the ethylene grafted polymers, and their ultimate use in liquid petroleum hydrocarbon oils such as residual fuels or reduced crude oils for improving the aforementioned properties of such liquids.

Normally liquid hydrocarbon oils including lubricating oils and petroleum middle distillates such as kerosene, No. 2 heating oils, residual oils, Diesel fuels, and jet fuels, or reduced crude fractions of waxy nature, have,

,for many years, been treated with additives designed to inhibit or minimize radical changes in their physical characteristics which are dependent upon the variations in temperatures to which they are atmospherically or artificially subjected. These considerations are particularly significant in the case of oils and oil fractions originating from petroleum sources which contain parafiinic and/or Waxy constituents. In order for a hydrocarbon fuel to be utilized effectively, it must have the property of being freely fiowable through conduits, both from the standpoint of conducting the same to the burner or carburetor by which means it is combusted and if exhibiting free flowing properties and anti-wear properties in handling, storage, pumping, transportation, etc. In regions where seasonable atmospheric temperatures are below 30 F., problems have been encountered in all of these respects. Oils which contain sizeable quantities of waxy components have a tendency to precipitate the wax as large interlocking crystals which trap the fuel or oil into a gel-like structure which has a tendency to markedly increase the viscosity of such fuels and oils upon a lowering of the atmospheric temperature. Such conditions cause the fuel or oil to solidify or tend to have much higher viscosity such that, for all practical purposes, the hydrocarbon oils become nonpumpable, exhibit higher wear qualities to pumps, and, in fact, even become nontransportable. This gel or solidification condition is generally known as the pour point and arises largely by reason of the tendency of the wax crystals to form an interlocking network. This tendency of the crystals to form such networks tends to plug fuel filters, and to increase the wear on pumps handling such products to the point where it becomes impractical at these low ambient temperatures to handle, transport and market such hydrocarbon oils.

3,462,249 Patented Aug. 19, 1969 In almost all instances where such hydrocarbon products are conducted through pipes, filters are incorporated for the purpose of removing sediment or extraneous materials which per chance are or become associated with such oil fractions. Such filters are necessarily of fine pOre size so as to effectively remove fine particles from the oils so handled or transported.

In the past, various types of additives have been suggested for these hydrocarbon oils for the purpose of depressing the point at which the hydrocarbon oil solidifies, becomes nonpumpable, or becomes so viscous that the transporting pumps are seriously impaired in their operation. Such substances have been termed pour depressants. Their function has been to inhibit the crystallization and crystal growth of the waxy parafiinic components contained in the oils. Lubricating oils have had their pour points drastically lowered in the past through the addition of small amounts of various, now conventionally employed, pour point depressant additives. More recently, fuel oils, Diesel oils, reduced waxy crudes, residual oil fractions of a wax nature have had various additives incorporated into their compositions in small amounts for the purpose of lowering their effective pour points and for improving their pumpability and flowability in transportation lines.

In particular, minor amounts, i.e., from 0.01 up to 5 wt. percent of a relatively low molecular weight copolymer of ethylene and vinyl acetate have been commercially and extensively employed to improve the handling of middle distillate oil fractions under atmospheric temperature conditions of 20 F. or below. Many prior disclosures with respect to this development are known, among which are US. Patents: 2,499,723, 2,654,188, 3,048,479, 3,093,723, 3,126,364, and 3,236,612. The transportation and movement of such oil fractions at temperatures at or near the cloud point of the particular oil fraction involved is believed to result in the initial formation of small wax crystal nuclei but if that temperature is maintained over a considerable period of time these initial crystalline nuclei have a tendency to grow forming large crystals and so the tendency is for the material to become troublesome in its transportation or its passage through oil lines. The continued growth of the initial crystalline nuclei at the oils cloud point increases the viscosity of the oil markedly and thus requires the expenditure of far more energy to transport the fuel than would be the case of such initial crystals remained small and would not increase in size.

The novel ethylene grafted polymers of the present invention have been found effective in changing the size of the wax crystals which precipitate from the hydrocarbon oils both initially and as the temperature is lowered thus resulting in more crystals of much reduced size than in cases where these novel ethylene grafted polymers are not incorporated into such oils.

The polymers per se, as before stated, are, for the most part, already well known and in the past have been employed as additives for hydrocarbon oils. The present invention utilizes these materials as starting materials into which ethylene is incorporated by an ethylene grafting polymerization technique so that the ethylene grafted polymers, by reason of ethylene grafting technique em ployed, thereafter possess the same long chain portions of the polymer and, in addition, possess pending therefrom at numerous points, depending upon the relative activities of the carbon atoms in the alkyl chain, a plurality of polyethylene chains attached thereto so that an increased branchiness in the character of the original polymer as well as an increased number average molecular weight, is achieved. The resultant ethylene grafted polymers, surprisingly, exhibit more eflicacious pour point depressant characteristics than do the original polymers while, at the same time, they do not sacrifice combustion qualities in the middle distillate fractions or the desired lubricity and viscosity qualities in the lubricating oil, reduced crude, and heavy oil fractions.

The polymers which serve as starting materials from which the ethylene grafted products are produced are of varied nature. They may or may not possess olefinic unsaturation and they have a number average molecular weight between about 800 and about 50,000. The following types of classes of polymers are contemplated as starting materials onto which ethylene may begrafted by a chain transfer type of polymerization reaction:

(1) Homopolymers of C to C alpha mono olefins,

(2) Copolymers of C to C alpha mono olefins with a different alpha mono olefin selected from C to C mono olefins, with an alkyl (mono or di) ester of an alpha, beta olefinically unsaturated dicarboxylic acid or anhydride, with a vinyl ester of a fatty acid, or with C to C alkyl esters or acrylic or methacrylic acid,

(3) Homopolymers of vinyl esters of long chain (C to C faty acids, or of C to C alkyl esters of acrylic or methacrylic acid,

(4) Copolymers of the monomers of (3) with a vinyl ester of a fatty acid, with mono or dialkyl esters of alpha, beta olefinically unsaturated dicarboxylic acids or anhydrides, or with C to C alkyl esters of acrylic or methacrylic acid,

Copolymers and terpolymers of the monomers of (2), (3), or (4) with N-vinyl pyrrolidone, N-vinyl pyridine, vinyl quinoline and their lower C-alkyl derivatives such as 5 ethyl 2 vinyl pyridine and 2-methyl-5-vinyl pyridine.

Exemplary of the polymeric reactants that may be employed as starting materials are the following: (copolymers are shown thus: monomer A-monomer B) polypropylene, polyisobutylene, 2-ethylhexyl acrylate-methyl arcrylate, n-octenel-isobutylene, propylene-pentene-Z, propylene dilorol fumarate, propylene cetyl maleate, propylene-didodecyl fumarate, propylene-dodecyl methacrylate, isobutylene-di-n-decyl fumarate, n-vinyl pyrrolidone-lauryl methacrylate, n-vinyl pyrrolidone-mixed alkyl acrylates (i.e., cetyl acrylate and octadecyl acrylate, or dodecyl methacrylate, and n-hexyl methacrylate, etc.), stearyl methacrylate 2 methyl 5 vinyl pyridine, terpolymer stearyl methacrylate-lauryl methacrylate 2 methyl-S-vinyl pyridine, polyvinyl laurate, polyvinyl oleate, vinyl acetate-vinyl laurate, vinyl stearate-vinyl decanoate, vinyl butyrate-vinyl rstearate, lauryl acrylate-ethyl acrylate, C oxo acrylate-butyl acrylate, vinyl acetatealkyl fumarates such as di C alkyl fumarate or mixed ethyl fumarate plus di C alkyl fumarate, vinyl acetateoctyl fumarate, vinyl laurate-lorol fumarate, vinyl acetateoctadecyl fumarate, tallow fumarate-vinyl acetate, isobutylene-styrene, isobutylene-ethyl fumarate, octadecenelauryl maleate, propylene-maleic anhydride, propylene diethyl fumarate, cetyl fumarate-octadecyl methacrylate, diethyl aminoethyl methacrylate-lauryl methacrylate, 2- hydroxy ethyl methacrylate-mixed stearyl and lauryl methacrylates, styrene-lauryl acrylate, lauryl maleatelauryl methacrylate, ethyl acrylate-lauryl methacrylate, methyl acrylate-dodecyl maleate, isopropenyl acetatetetradecyl acrylate, polymethyl-methacrylate, polylaurylacrylate, and polyoctyl methacrylate.

The resultant ethylene grafted polymers or copolymers are generally viscous, heavy, whitish liquids or semisolids having a number average molecular weight substantially above that of the starting polymer, i.e., between about 800 and about 50,000. A number of patents disclose the method by which the aforementioned polymers and copolymers may be formed and exhibit representative teachings of the methods of producing such polymers which have heretofore been found useful in the treatment of lubricating oils and/or middle distillate fuels. As examples, the following patents are noted: 2,327,705,

2,746,925, 3,060,120, 2,721,879, and 2,600,385, as well as many others that could be mentioned. The present invention does not reside in the formation of the polymers or copolymers nor any improvement in their process of production. All are formed by conventional polymerization techniques using free radical, cationic, or Ziegler type catalysis or initiation.

The same type of free radical polymerization may be employed in the preparation of one type of polymer as well as employed in the grafting of the polymer with ethylene. In general, conventional alkyl, acyl, and aroyl peroxides are employed. These are conventional promoters. Representative of this class are the following: benzoyl peroxide, dicumyl peroxide, tertiary butyl peroxide, tertiary butyl hydroperoxide, tertiary butyl perbenzoate, lauroyl peroxide, acetyl peroxide, peroxy dicarbamate, dichloro-benzoyl peroxide, and alpha,alpha, azo-di-isobutyro nitrile, etc. No particular significance needs to be attached to the selection of a specific peroxide; it being well within the skill of the average polymerization chemist to select a peroxide which has a suitable half-life corresponding to the particular temperatures employed in effecting either the original polymerization or in effecting the ethylene grafting of the resultant polymer or copolymer which is the starting material in this latter operation.

The reaction conditions employed are generally as follows: a temperature of between about and about 500 F., depending upon the choice of free radical promoter, and sufiicient pressure to maintain the reaction 1 in a liquid phase and to provide a suflicient concentration of ethylene in solution. The solvent employed may be an aromatic solvent such as benzene, toluene, or the like or it may be, for example, an aliphatic solvent such as carbon tetrachloride, hexane, heptane, or mixtures of the lower aliphatic hydrocarbons.

The reaction is carried out for varying periods of time depending upon the type of substrate and the degree of branching desired but usually requires from about 2 to about 8 hours, preferably between about 3 and about 5 hours. Pressures of from 50 or p.s.i.g. up to about 3,000 p.s.i.g. are generally satisfactory although higher pressures may be employed if they are necessary in order to maintain a sufficiently high ethylene concentration and liquid phase conditions. Sufiicient pressure is employed in order to maintain a liquid phase reaction medium. Stainless steel pressure vessels equipped with stirrers are ordinarily employed and in the ethylene grafting reaction the pressure is maintained continuously by the application of ethylene pressure from a suitable source. The reactor is charged with solvent and polymer and brought up to the desired temperature. The desired pressure is generally maintained by means of the introduction of ethylene, either continuously or intermittently, throughout the duration of the reaction. The peroxide in solvent is charged continuously to the reaction vessel. Preferably, the temperature is maintained between about F. and about 300 F. and the pressure will most generally be adequate if it is maintained between about 400 p.s.i.g. and about 1,200 p.s.i.g. Generally, the peroxide is employed in the reaction mixture to the extent of between about 0.05 and about 1.5 wt. percent of the total reaction mixture. This is not a critical amount for amounts outside this range may be employed.

At the conclusion of the formation of the ethylene grafted polymer, the pressure is reduced by flashing or by other means of reducing the pressure and the reactor contents are emptied, stripped of solvent and unreacted reactants either by distillation under vacuum or at atmospheric pressure, after which the ethylene grafted polymer is usually redissolved in a suitable diluent oil for convenience in handling and shipping. As a result of the ethylene graft, there is usually a 10 to 20% increase in molecular weight of the original polymer or copolymer corresponding with the increased branchiness of the ethylene grafted copolymer.

Oftentimes there is no need to recover the grafted copolymer from its reaction mixture or in the alternative to completely distill off the solvent associated with the reacted mixture and a liquid concentrate of the grafted copolymer may be employed directly as the additive for fuel oils and for lubricating oils.

In general the amount of ethylene incorporated into the copolymer by grafting will range between about and about 20 wt. percent based upon the weight of the original polymer or copolymer. Preferably, ethylene is incorporated to the extent of about wt. percent on the same basis. The polymer so grafted generally has its effectiveness increased over the ungrafted polymer. For example, 0.02% of a particular ungrafted copolymer in any given oil will not depress the pour point of a middle distillate heating oil. The use of the same amount of the ethylene graft of the same copolymer in the same oil will result in the reduction of the pour point to the extent of about 10 to F.

The petroleum oil fractions to which these ethylene grafted polymers or copolymers are added are the hydrocarbon middle distillate fuels such as kerosene, No. 2 heating oil, diesel fuels, jet fuels, the residual heating oils, and the reduced crudes obtained from waxy or parafiinic crude oils. The middle distillate fuels generally have a boiling range of between about 250 F. and about 800 F. while the lubricating oil fractions have a boiling range of between about 650 F. and about 1,100 F. In the case of these fuel oils, the amount of additive employed generally ranges between about 0.01 and about 5.0 wt. percent, and in the case of lubricating oils, the amount of novel additive therein will range between about 0.01 and about 10.0 wt. percent.

These additives may be employed alone or in combination with other well known additives for hydrocarbon fuel oils or lubricating oils such as other pour depressants, e.g., the commercially available ethylene-vinyl acetate copolymers or other commercially available pour point depressants, viscosity index improvers, corrosion inhibitors, antioxidants, and the like. Among such viscosity index and pour point agents may be mentioned the high molecular weight polymers Acryloids and Paraflow, i.e., chlorinated wax-naphthalene condensation products, isobutylene polymers, acrylate or methacrylate polyesters and the like. The corrosion inhibitors are those customarily employed such as the inorganic or organic nitrites, for example, sodium nitrite or lithium nitrite, diisopropyl ammonium nitrite or dicyclohexyl ammonium nitrite, the metallic organic phosphates, for example, calcium or zinc dicyclohexylthiophosphate or the same salts of methyl-cyclohexylthiophosphate; antioxidants such as the commercially available and conventionally used phenols and amines such as octadecylamine, 2,6-di-tertiary-butyl- 4-methyl phenol; or even in association with the extreme pressure additives such as the conventional organic phosphites and phosphates.

In the following examples, aliquots of the ethylene grafted copolymers were compared with the same ungrafted copolymers in a middle distillate heating oil in order to determine the extent of the pour point depressing action. The pour point determinations were performed in accordance with ASTM D-97. A sample in each instance was cooled systematically under quiescent conditions and observed at intervals of approximately 5 F. of temperature lowering. The pour point is the lowest temperature at which the oil flows when the container is tilted.

The following examples are given as illustrations of the invention but it is not intended that the invention be limited thereby.

EXAMPLE 1 500 grams of polyisobutylene of about 800 number average molecular weight and 1,125 cc. of benzene were charged to a pressure reactor. 1,100 to 1,150 p.s.i.g. of

ethylene was thereafter maintained on the reactor which was heated to 150 C. for 2% hours. 23 wt. percent concentration of di-tertiary butyl peroxide in benzene was added at the rate of 30 cc./hr. throughout this time. At the end of this time the temperature was lowered, the reactor vented, and the product worked up by removing the solvent on a steam bath. 800 grams of ethylene grafted polyisobutylene was obtained. 0.02 wt. percent of this grafted polymer lowered the pour point of at 0 F. pour point heating oil by 15 degrees.

EXAMPLE 2 500 grams of polypropylene having a number average molecular weight of 843 was charged to a pressure reactor in 1,125 cc. of benzene and a 23 wt. percent concentration of di-tertiary butyl peroxide in benzene was added thereto at the rate of 30 cc. per hour for 3 hours and 25 minutes, during which time ethylene pressure was maintained on the reactor to the extent above specified. At the end of this time the reactor was cooled and the pressure gradually released. The product was worked up as in Example 1. There was recovered from the reactor mixture 693 grams of ethylene grafted polypropylene having a number average molecular weight of about 975. 0.02% of this grafted polymer lowered the pour point of a 0 F. natural pour point heating oil by 10 degrees.

EXAMPLE 3 153.7 grams of a copolymer of 2-ethyl hexyl acrylate and methyl acrylate, and 1,000 grams of benzene were charged to a pressure reactor essentially according to the procedure of Example 1. An ethylene pressure of 1,150 p.s.i.g. was maintained for about 1 /2 hours, during which time 45 cc. of 23.0 wt. percent solution of ditertiary butyl peroxide in benzene were added. 257 grams of ethylene grafted copolymer were obtained. The following table shows the comparative pour potency of the grafted and ungrafted copolymers in a typical heating oil.

ASTM pour point, F.

Natural pour point 0 0.1% ungrafted polymer 5 0.1% grafted polymer -20 As used in this description and accompanying claims, the term polymer is intended to include homopolymers, copolymers, and terpolymers.

Having now thus fully described and illustrated the invention, what is desired to be secured by Letters Patent 1s:

1. A composition comprising a major amount of petroleum oil selected from the group consisting of middle distillate fuels, residual fuels and reduced crude oils, and about .01 to about 5 wt. percent of a pour point depressant formed by grafting ethylene onto a hydrocarbon oil soluble polymer of polymerizable, monoolefinically unsaturated organic monomers, said polymers having a number average molecular weight of between about 800 and about 50,000, the grafting reaction being promoted with a free radical polymerization promoter at a temperature of between about F. and about 500 F. under at least sufficient superatmospherie pressure to maintain a liquid phase reaction medium.

2. A composition comprising a major amount of p troleum oil selected from the group consisting of middle distillate fuels, residual fuels and reduced crude oils and about 0.1 to 5.0 wt. percent of a pour point depressant and flowability improver prepared by a process which comprises reacting ethylene with a hydrocarbon oil-soluble polymer having a number average molecular wt. between about 800 and about 50,000 selected from the group consisting of: (l) homopolymers of C to C alpha monoolefins, (2) copolymers of C to C alpha monoolefins with a compound of the group consisting of a different C to C alpha monoolefin, an alkyl ester of an alpha, beta olefinically unsaturated dicarboxylic acid,

an anhydride thereof, a vinyl ester of a fatty acid, a C to C alkyl ester of acrylic acid, and a C to C alkyl ester of methacrylic acid, (3) homopolymers of vinyl esters of C to C fatty acids, homopolymers of C to C alkyl esters of methacrylic acid, (4) copolymers of the monomers of (3) with a vinyl ester of a fatty acid, with an alkyl ester of an alpha, beta olefinically unsaturated dicarboxylic acid, an anhydride thereof, with C to C alkyl esters of acrylic acid and with C to C alkyl esters of methacrylic acid, and copolymers of at least one of the monomers of (2), (3) and (4) with a vinyl compound selected from the group consisting of N-vinyl pyrrolidone and N-vinyl pyridine; the reaction being promoted with a free radical polymerization promoter at a temperature of between about 900 F. and about 500 F. under sufficient pressure under the reaction conditions obtaining to maintain a liquid phase reaction medium.

3. A composition as in claim 2, wherein said oil is a distillate fuel oil.

4. A composition as in claim 2, wherein said oil is a residual fuel oil.

5. A composition as in claim 2, wherein said oil is a reduced crude oil.

6. A composition as in claim 2, wherein the hydrocarbon oil-soluble polymer is polypropylene.

7. A composition as in claim 2, wherein the hydrocarbon oil-soluble polymer is polyisobutylene.

8. A composition as in claim 2, wherein the hydrocarbon oil-soluble polymer is a polymer of C to C alkyl ester of acrylic acid.

References Cited UNITED STATES PATENTS 2,379,728 7/1945 Lieber et a1. 4462 XR 2,543,964 3/1951 Giammaria 25256 2,544,376 3/1951 Butler 25256 2,957,854 10/1960 Lorensen et 211.

3,048,479 8/1962 Ilnyckyj et a1. 44-62 3,260,728 7/1966 Ilnyckyj 4462 XR FOREIGN PATENTS 807,737 1/ 1959 Great Britain. 822,632 10/1959 Great Britain.

DANIEL E. WYMAN, Primary Examiner W. J. SHINE, Assistant Examiner U.S. Cl. X.R.

"H050 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 2,2 9 Dat August 1%4960 Inventor(s) Norma-1'1 Tunkel It is certified that error appears in the above-identified patent l and that said Letters Patent are hereby corrected as shown below:

r- 001. 7, claim 2, line 15, cancel "900" and substitute --90--.

SIGNED HND SEALED JUL 1 4 1970 Atteat:

Edward M. Fl

ffi wmum E. sum, .13. AW 0 cer I flomissioner of Patents 

